1. Field of the Invention
The present invention relates generally to automated bonding and packaging of integrated circuits and, more particularly, is concerned with an improved method for curing epoxy encapsulant on integrated circuit dice for forming integrated circuit packages. Disclosed is an improved interleaver tape and process for use thereof in protecting epoxy encapsulated integrated circuit dice during heat curing.
2. Description of the Prior Art
An improved method of bonding and packaging integrated circuits is known as tape automated bonding ("TAB"). An example of such a method to which the present invention can be advantageously applied is described in U.S. Pat. No. 4,689,875 assigned to the assignee herein. In the method as taught therein, chips are bonded to a carrier tape to provide a supply of dispensable integrated circuit packages. Carrier tapes are then stored on reels for use in automated operations. As part of the process of producing these packages a tape is adapted in desired patterns for receiving dice. Such patterns include small, flat fingers or leads in a copper layer of the tape which fan out to wider leads. Portions of the tape surrounding the leads will be removed during later processing.
An integrated circuit is positioned above a desired pattern so that the contacts are aligned with the small fingers or leads. The pads are then thermally bonded to their respective leads simultaneously. The bonding operation can involve a large number of leads and pads.
After bonding is completed, the integrated circuits remain attached to the tape by the bond between the contact points and the fingers as well as elements of a support structure left in the carrier tape. At a desired time, the leads and support structure are cut and the circuit is removed from the tape.
Integrated circuits bonded to a carrier tape by the TAB process allow integrated circuit components to be provided on a reel that may be used in automated assembly operations. Integrated circuits may also be transported on such reels to desired locations for testing, assembly and the like, protected against mechanical abrasion and damage. Utilization of a TAB system increases production and provides an economical and reliable means for assembling and bonding integrated circuits, and a protected mode for transporting the final product.
Prevention of mechanical damage to an integrated circuit begins with packaging and protecting an integrated circuit on a carrier tape. The carrier tape will comprise at least two layers, including one of an electrically conductive material, which includes small flat leads. The support structure comprises a carrier bridge or frame of the non-conductive material. Leads of the integrated circuit are cut at a predetermined length from the integrated circuit and outside of the frame.
The electrical contact points between the dice and their respective leads is then coated with an epoxy material to provide insulation and encapsulation. Epoxy encapsulation is the primary way of protecting integrated circuit dice from mechanical damage.
However, epoxy encapsulation materials require heat curing. While it would be convenient to wind immediately the carrier tape with the freshly encapsulated integrated circuits on a reel, such has proven difficult without first curing the epoxy. Should the epoxy come into contact with other materials or structures before curing, the epoxy may adhere to that other material upon curing. Because full curing requires baking the integrated circuit packages for several hours at an elevated temperature, carrier tapes have been cut into relatively short lengths to allow introduction of tape segments to curing ovens for heating. Thereafter, the tape is reconstructed and wound on a supply reel for transportation.
Interleaver tape has been used in the industry to protect carrier tape from mechanical damage during transportation. The carrier tape and interleaver tape are wound on a reel in alternating layers. The edges of the interleaver tape are corrugated so that only edge corrugations of the interleaver tape abut against the carrier tape. Thus, the integrated circuit dice are held spaced from the body of the interleaver tape, giving the desired protection against mechanical damage from abrasion or impact.
Prior art interleaver tapes are made from plastic materials capable of supporting corrugation. However, plastic does not provide protection against static electricity present in manufacturing environment. At least one supplier of prior art interleaver tape has supplied plastic interleaver tape with an aluminum coating to prevent development of static charges.